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MrSeb writes "Back in the olden days, when WiFi and Bluetooth were just a glimmer in the eye of IEEE, another short-range wireless communications technology ruled supreme: Infrared Data Association, or IrDA for short. IrDA was awful; early versions were only capable of kilobit-per-second speeds, and only over a distance of a few feet. Trying to get my laptop and mobile phone to link up via IrDA was, to date, one of the worst tech experiences I've ever had. There's a lot to be said for light-based communications, though. For a start, visible (and invisible) light has a frequency of between 400 and 800THz (800 and 375nm), which is unlicensed spectrum worldwide. Second, in cases where you really don't want radio interference, such as hospitals, airplanes, and other sensitive environments, visible light communication (VLC), or free-space optical communication, is really rather desirable. Now researchers at the National Taipei University of Technology in Taiwan have transmitted data using lasers — not high-powered, laboratory-dwelling lasers; handheld, AAA-battery laser pointers. A red and green laser pointer were used, each transmitting a stream of data at 500Mbps, which is then multiplexed at the receiver for a grand total of 1Gbps."

While the technology is old, the implementation seems to be new. Also, the form it has taken means that we are likely to see cheaper commercial solutions coming out or a whole bunch of hobbyists implementing this themselves - or both. $100 vs $4000+. I can just imagine mesh networks based on this.

If these can be coupled with solar power and are of low energy use, then I can imagine these being alternative solutions to laying cables in remote areas.

For enterprise purposes, the equipment costs these days are lower than they used to be and still falling. Eventually, though, an "industrial quality" system of this type will hit a pointy where the hardware cost is inconsequential, because the actual cost of operating such a unit is really in the support contracts, unless you are big enough to have a trained FSO/RF specialist on staff and stock backup units. (Many of these FSO units these days are hybrid units that use microwave and FSO to provide technol

For mesh networks, we really need one of the former TV channels. Fat chance they let us do it; we could subvert the entire system they've built on the dark backend which they use to monitor everyone. A true Little Brother TV channel mesh network wouldn't need the internet backbones, not if it were cheap, easy, and used its own protocols. So it will be illegal. But, as I said elsewhere on the talkback, don't let that stop you.

If these can be coupled with solar power and are of low energy use, then I can imagine these being alternative solutions to laying cables in remote areas.

The range is only 25 meters. it is much cheaper to lay 25 meters of cable and a repeater every few kilometers than a laser repeater every 25 meters. If a single repeater goes out the whole line is down. Basically one would have 40 failure points every kilometer. Say one is 10km from the nearest hard line that means 400 repeaters and 400 possible points of failure.

You're missing the point. The summary clearly states that the interesting point here is that it was done with cheap 10$ laser pointers that you can buy from Amazon. Yes, this was old tech - if you were willing to shell out 15k for high end gear. The fact that it can be reproduced for a much lower price (maybe a few hundred at most by the time you get integrated units and pay for research?) and therefore more likely to see more widespread usage, is the point.

The reason the available commercial equipment for this stuff is expensive has nothing to do with the quality of the laser, though (the site GP linked to specifies the laser in their entry level device as being a 7mW laser diode, so probably about 50% more powerful than the lasers used in the OP's article). The point is that it's expensive because the only application it's viable for is inter-building linkage, which *almost nobody wants to do*. You can't use it to replace ordinary wireless networks, becaus

I'm pretty sure that if you got the price down to about $50, people would find a lot more uses for this, including sharing network connections with friends (in particular in rural areas), secure communications, and distributing access points. Not everybody lives in cities with otherwise excellent coverage.

I'm pretty sure that if you got the price down to about $50, people would find a lot more uses for this, including sharing network connections with friends (in particular in rural areas), secure communications, and distributing access points. Not everybody lives in cities with otherwise excellent coverage.

I don't think it'd be useful for those applications. Reading TFA, this device has a useful range of approximately 10m, which is somewhat limiting. Even without this limit, houses in rural areas are unlikely to have undisturbed line of site. Birds will be a problem (current commercial systems solve this by using redundancy to allow routing around birds, I believe, which makes your $50 an unrealistic target price). To make these things work properly, they really need to be on top of tall buildings to ensu

Even at $100 it may still be cheaper than digging up the ground and laying fibre optics in certain cases. I think what would really change things is if these were easily installable by someone who isn't a specialist.

Using a laser transmitter would require the receiver to stand in exactly the right place, only one receiver could use the system at a time, and transfers would be interrupted by accidental movements. It would be too hard to use for anyone to actually want to use it.

Either 802.11g/n or bluetooth could be used for the purposes you describe and would be much more convenient for everyone involved.

What you want will be provided by 802.11ad, which will essentially offer little WiFi bubbles with bluetooth-like range. The only thing lacking, in fact, to doing it over existing WiFi frequencies is some sort of widely-implemented standard for putting the SSID to join for these info blurts into the QR code.

because everyone wants to go through the hassle of joining 150 different wifi networks while they are at a museum. That is where the laser idea makes sense. So you make a cradle 'touch your phone here to download this display's audio clip' You sandbox all the data that comes in from that port, and do away with cumbersome 'join this network?' notifications.

But then these guys can mostly just dig up the land between their buildings and lay cables, which will give higher capacity and more reliability (one of the universities has an issue because one of their buildings is separated from the rest by a public road... they might benefit from this).

You could spend $50 a lot of times vs digging up land between buildings and laying cables, so if capacity and reliability is a problem, just buy 10x for greater capacity and reliability, or even 100x would probably still be cheaper than digging and laying cables.

Hardware is just a small part of the cost. There is installation and maintenance. The cost of going more than 25M includes installing a pole ever 25m, getting power to the poles and maintaining the repeater on top of the poles. Even solar panels need to be cleaned regularly. Would you rather maintain 2 switches inside buildings and 100M of cable or 16 laser nodes( for redundancy) of which 12 are on top of poles with attached solar panels? All it takes to bring this network down is for a birds with long tai

I can think of another use:Temporary in-room networking where security or bandwidth conjestion are a concern. I could envision a server room issue where you needed to understand what was happening at multiple points in your network that aren't normally tapped. You use something like a vampire tap and a raspberry pi to get copy off the data, analyze, and send back to something like splunk. However, rather than running temporary wires all over, instead send them by laser to the central monitor. Then when

Radio hams have been experimenting with point to point communication by light. It's been mountain-top to mountain-top so needs quite precise alignment. Also the data rates have been quite low - more voice. But the technique is quite old. We've known about modulating laser diodes for some time.

A quick search reveals this site reporting a 104 mile link using LEDs. http://www.bluehaze.com.au/modlight/

"The problem is, the bits are all coming out a kilometer away, and the printer’s down here at the other end, so how do we get the data to this thing?

So, we sat down one time and said, "So why don’t we make an optical link?" Because we looked at doing microwave, but those were only three megahertz, and you’ve got to get enough FCC permission to do that, even then. So the interesting thing is there are no communication

This does make me wonder, however, if we could see fiber optic gbics that don't cost thousands of dollars each if the technology that makes this free-air communication possible can be adapted to fiber optic applications.

I had assumed an LX range with mode conditioning, and on top of that I had assumed that something that could work through a medium as imperfect as ambient air with ambient light and still achieve speeds of half a gigabit could achieve much faster speeds over the controlled conditions of cable, like say, 10gb over laser-optimized OM3... Which are currently thousands of dollars.

Laser based FSO isn't exactly a new field.1Gbps data rate with a diode laser isn't that hard to achieve even with pretty simple drivers and 1-bit amplitude modulation.Neither is using wavelength multiplexing some revolutionary new idea.So... huh?

OK, you try turning this into a viable commercial product at a lower cost than the competition. The problem is, this is a niche market because these things are really hard to find a suitable application for. You'll be setting up a manufacturing base and then selling maybe 1000 units per year, so you need to offset the cost of manufacturing, support staff, sales staff, development.... hence you'll be selling each unit for $1000 or more. Probably much more, because to make it useful you'll need precision m

Well, that's what I thought until I tried. Connected a laser pointer to a signal generator and measured its light output. As the frequency increased above about 1 MHz, the modulation level decreased to a non-usable level.

Ok, the real question is... how does this apply to/.'s new BI focus? Can I use this instead of spreadsheets or specialized software to properly align my Business Intelligence with the synergies of the corporation for maximization of profitability?

Got a source on that? Laser diodes don't "wear out" as far as I am aware. They may be damaged by thermal runaway in the short term or long term by poor design but the only critical factors here is the stability of the current source, choice of bias point, and thermal design. They certainly don't get tired over time.

I assume that laser diodes are no more fundamentally resistant to degradation over time than ordinary LEDs are. Not a huge problem(LEDs are usually specced to be something like 80% of original output after 100,000 hours); but solid state devices only look immortal compared to their mechanical counterparts.

That would be a MASER (microwave, not light), and they predate lasers. However, a maser holds no advantage over a regular microwave transmitter for terrestrial communications. The distance of point to point microwave links with standard radio technology is limited by the curvature of the earth, not power or beam divergence. Even with tall towers, it's very hard to obtain a line of sight path between two points on earth more than about 50 miles apart.

Beam divergence [wikipedia.org] is a bitch at low frequencies. EM signals don't travel in a straight line, a ray of them tends to get wider over distance. This effect is stronger at low frequencies. For space you need the highest frequencies you can get if you want to have some usable distance. Gamma lasers would be preferable, if it were possible to make those. Or you'd need a very wide beam and thus a very large laser/maser.

Even with tall towers, it's very hard to obtain a line of sight path between two points on earth more than about 50 miles apart

That was a big disadvantage with MASERs. However, what I propose, is data transfer using high-powered LASERs. Initial handshaking will be done by "creating" a line of sight path before communications can start in lower-power mode:D

It's only a matter of time before the MPAA/RIAA gets this outlawed because pirates could be using it to broadcast entire ripped DVDs to each other in mere seconds using sharks with frickin' multiplexin' red and green lasers attached to their heads! You laugh, but it will happen. [slashdot.org]

A proof of concept on laser pointer networking was done two years ago, if you are interested seehttp://www.diva-portal.org/smash/record.jsf?searchId=4&pid=diva2:325270 - Fulltext athttp://www.diva-portal.org/smash/get/diva2:325270/FULLTEXT01

I'm surprised the cell phone companies haven't implemented something similar on their towers to reduce backhaul. Have dozens of towers in a given area relay optically to a super node tower with amazing backhaul. Have them relay to a few others in a standard mesh network layout for redundancy. Might even reduce their spectrum need if they are using channels to talk tower to tower. May have some issues with rain I suppose though, but that could be mitigated if laser wavelengths for which water is not refractive exist. Or just use laser arrays with heavy multiplexing and parallel signal reinforcement.

Visible line-of-sight issues ruin the possibility in many applications. Rain is murderous to low-power visible light connections, as is fog and snow. Even wind will affect a laser-based length over any substantial distance as the end-points sway (and yes, all towers sway in the breeze).

Meanwhile, cell towers quite commonly already link with microwave: The big parabolic reflectors covered with fiberglass radomes that you see on many (perhaps most, or nearly all) cellular towers are not for subscriber usage, but to link neighboring towers together. This is often done using licensed frequencies, though unlicensed bands are also used.

There are generally also redundant backhauls using copper or fiber or both, but I guess the point I'm trying to make is that cell towers -already- use wireless RF backhauls...and that the tech described in the article isn't likely to change that.

As it stands, resistance to rain-fade and other weather seems to be excellent, at least anecdotally: I've never experienced it, and I've carried a cell phone for at least 1.5 decades.

(Disclaimer: I work with RF and wide-area long-range wireless networking as part of my day job, though not necessarily with back-end cellular systems in particular. Just because optical networking seems like a general non-starter to me doesn't mean that it's unsuitable for the uses that you suggest.)

This must be why air-laser consumer tech never came out of Silicon Valley or the UK; instead we have fiber optics. They knew about fog, so they pointed their lasers through glass tubes.

This seems just another "maker fair" type story, the type of which gets old and annoying - (undereducated person) discovers (old technology) made from (cheap new technology) thanks to (smarter people who understand new technology). It's a step above my research paper on popsicle-stick bridges though.

For a start, visible (and invisible) light has a frequency of between 400 and 800THz (800 and 375nm), which is unlicensed spectrum worldwide.

My God! They're broadcasting my movies over an unlicensed, unregulated carrier! This MUST be stopped! This "visible" light will aid paedophiles, piracy, terrorists, drug dealers and all manner of criminality!

No worries, the visible light spectrum is already being regulated. If you don't believe me, feel free to set up a 1500 watt spotlight pointing towards oncoming traffic on your street tonight. Let us know how it turns out.

A group of students at The University of Pretoria in South Africa did exactly this while I was still studying there, this was circa 2001.A large part of their motivation was to help build a technology for high-speed networks that were not subject to the state protected telecoms monopoly.

They used almost exactly the same technology, lazer-pointers for sending streams, but I believe they used solar-cells for receivers.

I remember they boasted speeds of over 1mbs which (back then) was incredibly fast (in fact faster than the internal buffers of the P2 computers they used - so that the data actually slowed DOWN after being received) but I don't believe they ever went beyond a single point-to-point connection.

Maybe one of the students who were involved is on slashdot and can give more details ?

Did you miss the location ? It was NOT slow if you were in South Africa. At that stage it still tended to take a while for US technology to reach the bottom of Africa. Hell, in some cases, it still does.

Hell most corporates here were still running on 10Mbps ethernet at the time.

I don't agree with the original poster about the deficiencies in IrDA.

This was in a time when dial-up access was the norm, if you were lucky you had ISDN, and your cellphone gave you patch 9600 baud connectivity. IrDA was fine in this situation.

I used my Nokia 6320 phone and Palm V to restart servers whilst on call from the comfort of restaurants, and even to make changes to Perl scripts from a different country. The range was poor, but fine, the performance was limited by the cellphone not IrDA.

I remember copying files from one laptop to another via the IR ports. There was an option in the BIOS (Dell) to chose between 'Normal IR' and 'Fast IR' and the latter gave something like 6Mbit I seem to remember, not sure, but it surely was fast enough to copy setups and iso's etc. Sure we were not allowed to move the laptops around in the meanwhile, but copying things was much faster over that link than using the 10Mbit network that was shared with the entire floor.Eventually we found out about using a dir

Sorry but this has existed as a communications system in the middle east and india for well over a decade now. People over there have been doing this with laser pointers and LED's for a very long time.

Granted it was only 100bt as it used existing transciver chips, but the jump to 1Gps is not that hard.

and why red and green? The existing designs all use RED for alignment and then IR for data comms so that it's not visible from acute angles.

Those with a (or even an) historical bent may be interested in the first outdoor optical communication system, the heliograph [wikipedia.org], which used reflected sunlight for long-distance communication via Morse code. The record distance covered was 183 miles (295 km), between Mount Ellen, Utah, and Uncompahgre Peak, Colorado on 17 September 1894.

To my knowledge, this record for terrestrial (i.e., non-moonbounce) optical communication has never been broken, even by modern laser and LED systems. The closest attempt [reast.asn.au] of

IrDA was the closest we ever came to solving the still-unsolved problem of how to transfer files wirelessly between two machines sitting next to each other. It's telling that the de-facto standard now is to carry around USB flash drives: god help you if you've lost whatever cereal-box prize you were using.

Compared to the dicking around we have to do with bluetooth - which, incidental

I had a BJC-55 for a while when I was using a laptop in my later high school years (back when - I presume - laptops were rare). Although it wasn't particularly practical, the fault had nothing to do with IrDA - which connected and setup on Windows pretty flawlessly.

I do remember it being quick enough that if I slid a device past the port, they'd link up and promptly delink when out of range pretty commonly.

So yeah - I'm in full agreement. It would be awesome if we could have a light-based gigabit data proto

Me and a buddy of mine cobbled together a Super Sekret Spi Laser Telephone System in highschool. It was a couple of cheap laser pointers and photovoltaic cells wired to the transistors in radio kits with microphones. They only worked well at night, over shortish distances, and were a complete bitch to aim. Still.. SUPER SEKRET SPI LASER PHONE!

I went to the paper, expecting to find a fairly high powered laser that is not a pointer, and expecting to call someone out on calling them pointers. However, they're only 5 mW, which is indeed a pointer. Cool that they can use such low powered lasers for this.

The FDA has regulations [fda.gov] in the U.S. saying that no laser products over 5 mW may be marketed as "pointers":

I don't know why this is being hyped so much... from my brief look it seems pretty dodgy.I'm not an expert in data transmission, but I have reviewed quite a few papers.

Two main points stand out:

1. They have two lasers of different wavelengths just so they can use the phrase "wavelength division multiplexing", but the lasers point at separate photodiodes! The lasers could be the same wavelength and it would make no difference.Doing this adds nothing to their paper and lowers my impression of the research qua

the one thing IrDa worked great for was using my HP Jornada with my HP 2100 printer.. was also nice to use the Jornada to print on campus because while they had the pay per page on lpr prints all the printers had an exposed IR port that would just blindly print what was sent. It was also useful to use my iPaq as an A/V Remote control.

what i never did understand is why it was a standard BUT placement and usable angle was never part of the standard.. I've got a 8525 that has it.. on the damn bottom of the phone... where it is completely useless.. and i remember a lot of laptops that put it on the side of the device and had no usable angle other than head on..

it wasn't a bad spec for the time and the proposed use (a wireless serial connection) but the implementations left a good bit to be desired..

Your comment reminded me of my old laptop and cell phone, both which had IrDA.

I never even thought about it, of course, until one day I set my cell phone down exactly line-of-sight to the laptop and both of the devices lit up and started talking to each other. The laptop even made a funny zap noise. Freaked me out.

Im reminded of my high school days- I had a laptop with irda (1998'ish) and the printer in our tech lab had irda as well. The printer had a print server attached that would queue up all the print jobs, but the irda port would take priority over anything in the queue. Our teacher had a vendetta against trees and would insist that we print everything, so about 5 minutes before class would end, everyone would start lining up at the printer. About 4 minutes before class would end, I would hit print on a 50-60 page Word doc and gloat to myself as everyone started freaking out. Yeah, i was a techno-douche.

I had a laptop where it as on the front edge.. even worse than the side.

I will say that irDa extended the life of an old HP printer i had, as the parallel port went belly up right after the warranty ran out , with the cost of a new formatter board being more than a new printer.

But only had 1 laptop with ir, so it was a pita when i wanted to print.. And had to do it on the kitchen table so it would get aligned properly...

Bluetooth is far more usable, except the lack of standard stacks.. the fact that they leave it to each manufacturer to implement each device profile in their stack as they see fit (ore more commonly not too) drives me nuts, It has gotten better as it has matured, but is something that should have never been allowed to happen.

Meh, we used what we had. The cool thing about using the PDA's though was that they also had IrDA *in* so we only needed about 3 minutes with a teacher's remote to program an entire new set of codes into it.

Except QAM and QPSK require a medium with a practically pure wave nature, pulse modulation of light is more a particle nature effect with the pluses of light consisting of numbers of individual photons each with their own specific frequency. The higher the data rate the fewer photons in each pulse.

Optical frequency division multiplexing is even more a particulate effect where the prism or grating effectively sorts the photons into individual streams. Though or course the fact that it works at all is actu

Well, of course they can, each wavelength of your signal there are billions of cycles of the carrier frequency and untold numbers of photons. Of course classical mechanics works perfectly fine in this state.

What the OP is talking about is trying to push the bit rate beyond the baud rate of the carrier by switching frequencies and phases mid cycle, this works wonderfully in the kHz range and is probably workable upto somewhere in the GHz range but if you try to do this to a signal of half an petahertz you